One set of goals of this project is to identify the changes in gene expression in various testis lesions induced by known reproductive toxicants, determine which cell types and mechanisms are altered after exposure to a toxicant, and define the sequence of changes in gene expression to separate earlier from later effects in testis lesions. We hypothesize that altered patterns of gene expression can be used to identify primary and secondary responses and to identify the initial target cell of a toxicant in the testis, and that the temporal pattern of changes in gene expression can be used to define the mechanisms of toxicity. These studies are identifying changes in patterns of gene expression in the testis in response to cadmium, a known male reproductive toxicant. Longer term goals are to determine the specific effects of different toxicants on gene expression in individual cell types of the testis, the time course of changes in gene expression induced by toxicants in different cell types of the testis, the patterns of changes in gene expression with different doses of toxicants, and the similarities and differences in the patterns of change in gene expression induced by other chemicals known or suspected to cause injury to the testis. Another set of goals is to prepare a mouse testis microarray that will be highly informative for studies of male reproductive toxicants, as well as for studies on effects of gene knockouts, endocrine manipulations, and other treatments. Eight cDNA libraries constructed with mRNA from mouse testis and germ cells isolated at different stages of development were subjected to single-pass sequencing from the 5' end to identify clones to be used for this purpose. Over 28,000 clones were sequenced and over 22,000 ESTs were deposited in public databases. A mouse testis 22K microarray has been constructed using this sequence information and other information public databases. Studies are underway to use this microarray to examine the effects of male reproductive toxicants on gene expression in the mouse testis.